This invention relates to a power transmission apparatus with two-phase type torque converter which may be favorably used in contruction machinery or the like where a large torque ratio is required.
In the case of a two-phase type torque converter having a first stator coupled to the output shaft and a second one fixed firmly, it is conventionally known well that a greater torque ratio than in the single phase type can be obtained by utilizing the reaction of the first stator so as to improve the working efficiency of construction machinery or the like and also to alleviate the speed change operation of the operator.
In FIG. 1 which shows a conventional composition of a two-phase type torque converter, a turbine 12 of a torque converter 11 is coupled to an output shaft 16 by way of central shaft 13 and gears 14, 15. A first stator 17 is coupled to a tube shaft 19 which is concentric with the shaft 13 by way of one-way clutch 18, while the tube shaft 19 is coupled to the output shaft 16 by way of gears 20, 21. A second stator 22 is fixed to a transmission casing 23.
In this conventional composition, however, when descending a steep slope under engine braking, the following problem occurs. That is, when the output rotating speed increases due to the inertial force of the vehicle, the one-way clutch 18 is disengaged automatically, so that the engine braking may be rendered ineffective. Or the car speed may fluctuate due to changeover of the idling and fixed states of the one-way clutch 18.
In this conventional composition, furthermore, while a great torque ratio is obtained, the transmission efficiency may be lowered in the idling region of the first stator 17 (in the high speed ratio region).
This invention possesses the following objects (a) and (b).
(a) To present a power transmission apparatus with two-phase type torque converter capable of enhancing the engine braking performance and preventing car speed fluctuations at the same time.
(b) To present a power transmission apparatus with two-phase type torque converter having high torque ratio and high transmission efficiency.
To achieve said objects, this invention, in a power transmission apparatus with two-phase type torque converter having a first stator coupled to the output shaft and a second one fixed firmly, is provided with a brake to fix the first stator and a clutch to disconnect between the first stator and the output shaft when said brake is in a released state.